In the United States, the Telecommunications Acts of 1992 and 1996 require that cable subscribers be given the option of owning the equipment required to receive cable services. To support competition in the market for so-called “host” devices (i.e. DTV receivers such as set-top boxes or integrated digital televisions), a Report and Order of the U.S. Federal Communications Commission (FCC) adopted on Sep. 10, 2003 and released on Oct. 9, 2003 entitled “Second Report and Order and Second Further Notice of Proposed Rulemaking” (referred to as the “Digital Cable Plug and Play Report and Order”), which is available at World Wide Web address hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-03-225A1.pdf and is hereby incorporated by reference hereinto, requires that cable operators make available security modules which are separable from host devices.
To satisfy the government's separable security requirements and to enable retail availability of host devices, point-of-deployment (POD) modules have been developed. A POD module (also known as a “POD security module” or simply a “POD”) is a hardware device (with embedded firmware) provided by a cable provider which is intended to be plugged into a host device (or simply “HOST”) to facilitate the display of digital television programs that are otherwise protected by the cable provider's conditional access (CA) scrambling system. When a POD module is plugged into a host device designed to receive such a module, subscribers are able to view the secure digital video services and/or listen to audio services for which they have subscribed, which services may include premium subscription channels. POD modules are sometimes referred to by the trademark CableCARD™. Physically, a POD module may be a Personal Computer Memory Card International Association (PCMCIA) card or a smart card device, both of which are approximately the same size as a credit card (although PCMCIA cards are thicker than a credit card). PCMCIA card are now also referred to as PC Cards. Specifically, a PC Card is 85.00 millimeters (mm) long (±0.10 mm), 54.00 mm wide (±0.20 mm), and has a 68-pin connector (two rows of 34 pins). A smart card (based on ISO 7810) is 85.72 mm long and 54.03 mm wide. A smart card may have a either 6-pin connector comprising Vcc, reset, clock ground, Vpp, and I/O, or an 8-pin connector comprising Vcc, reset, clock, Reserved, ground, Vpp, I/O, and Reserved.
POD modules serve two functions. First, the POD module acts as a descrambler, allowing the cable provider to be assured that the host device at the subscriber premises is a secure device without which scrambled content will be unviewable. Second, the POD module acts as a translator between the possibly varying out-of-band (OOB) protocols used on different cable provider networks and a single protocol (described below) that is expected by the host device. In other words, by virtue of the POD translation, the host device is only required to understand a single protocol, regardless of the OOB protocol (s) that may be operative on the cable provider network to which the host device is connected. Thus in the event of switching between cable providers or moving between different geographical areas, a subscriber should be able to continue using the same host device, provided that a new POD module is obtained from the new cable provider and plugged into to the host device. As well, this arrangement permits a cable provider to upgrade its network head-end without having to replace numerous set-top boxes at subscriber premises. The cable operator need only provide replacement POD modules in the event of an upgrade.
In a typical arrangement, a cable provider receives programming from various sources at its head-end and assigns it to channels. As defined in the American Nation Standards Institute/Society of Cable Telecommunications Engineers (ANSI/SCTE) 40 2004 Digital Cable Network Interface Specification standard, each channel is a unique 6 megahertz (MHz) section of the cable provider's bandwidth which in turn carries either a modulated digital signal that has been encoded to the Forward Application Transport (FAT) channel format or a modulated analog signal that has been encoded to the National Television Systems Committee (NTSC) format. At present, the FAT channel format specifies the use of ANSI/SCTE 54 2004 Digital Video Service Multiplex and Transport System Standard for Cable Television standard as the transport stream layer protocol for the digital signal. They are available at www.scte.org/documents/pdf/ANSISCTE402004.pdf and www.scte.org/documents/pdf/ANSISCTE542004DVS241.pdf respectively and are each hereby incorporated by reference hereinto. The numerous 6 MHz channels are then transmitted over cables simultaneously to subscribers in the form of an analog radio frequency (RF) signal.
The ANSI/SCTE 54 2004 standard further specifies the use of the MPEG-2 standard for transport stream formatting and video compression and the Audio Codec-3 (AC-3) standard for audio compression. MPEG-2 is a well-known video compression and transport standard developed by the Motion Picture Experts Group of the International Standards Organization and International Electrotechnical Committee Joint Technical Committee 1 Subcommittee 29 (ISO/IEC JTC1 SC29). AC-3 is well-known audio compression standard developed in the Advanced Television Systems Committee (ATSC) A/52B Digital Audio Compression (AC-3) (E-AC3) Standard. AC-3 is also referred to a Dolby® Digital which is a trademark of Dolby Laboratories, Inc. The AC-3 standard is available at www.atsc.org/standards/a—52b.pdf and is hereby incorporated by reference hereinto.
At the host device, an RF signal is received by a tuner within the host device. Depending upon the television channel selected by the subscriber (e.g. via a handheld remote control device), the tuner isolates one of the 6 MHz channels comprising the received signal and converts it to a fixed lower frequency. The output of the tuner is an analog signal representative of the tuned channel. This is referred to as a Forward Application Transport (FAT) channel.
The FAT channel is presented to a Quadrature Amplitude Modulation (QAM) demodulator within the host device. As is known in the art, a QAM demodulator converts the analog FAT channel to a baseband ANSI/SCTE 54 transport stream, which is a stream of (digital) packets. A subset of the packets of this stream represent the program content that is to be viewed by the subscriber (with the remaining packets consisting of control packets, “metadata” packets containing information about the network, and possibly other program content, as will be described).
In order to prevent unauthorized viewing of subscription channels, programs transmitted by way of ANSI/SCTE 54 transport streams are typically scrambled by the cable provider using a conditional access scrambling system. This is typically done for all but basic tier cable channels. The term “scrambling” is a legacy term which historically describes a technique developed in the 1970s whereby an analog cable television channel was reduced to a jumbled set of video images through removal of a synchronization signal or insertion of an interfering signal at the network head-end. In the digital ANSI/SCTE 54 transport stream, it is more accurate to refer to a program as being “encrypted” rather than “scrambled”, since digital encryption techniques (not the above-described approach) are now employed to encrypt packets. However, the term “scrambled” is still commonly used to refer to this network head-end encryption, and the term “descramble” is still used to describe decryption of this encrypted program.
An ANSI/SCTE 54 transport stream having scrambled content is forwarded to the POD module via the “HOST-POD interface.” The HOST-POD interface is also known as the CableCARD™-HOST interface. The HOST-POD interface is an interface governed by a standard known as the ANSI/SCTE 28 2004 HOST-POD Interface Standard. This standard defines the physical interface, signal timing, link interface and application interface of the HOST-POD interconnection (i.e. the interconnection between the POD module and the host device). The ANSI/SCTE 28 2004 HOST-POD Interface Standard is available at www.scte.org/documents/pdf/ANSISCTE282004.pdf, and is hereby incorporated by reference hereinto.
Assuming that a POD module is plugged into the HOST-POD interface of host device, the ANSI/SCTE 54 transport stream output by the QAM demodulator will be received at the POD module. At the POD module, two steps are performed. First, the scrambled program within the ANSI/SCTE 54 transport stream received from the host device is descrambled (i.e. decrypted). Second, the content is “copy protection” (CP+) re-encrypted and is provided back to the host device over the HOST-POD interface. The purpose of this re-encryption is to avoid unencrypted content from being transmitted, and possibly intercepted or copied, between the POD module and the host device. Re-encryption may be performed using the Data Encryption Standard (DES). DES is a method of data encryption which uses a private (secret) key that must be known and used by both the sender and the receiver of the data. DES is defined in the withdrawn U.S. National Institute of Standards and Technology (NIST) Federal Information Processing Standards (FIPS) Publication 46-3 (Electronic Code Book mode of operation). It is available at csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf and is hereby incorporated by reference hereinto. Packets representing minor channels that are not currently being viewed are passed from the POD module back to the host device unaltered.
At the host device, the CP+ encrypted ANSI/SCTE 54 transport stream is received at a transport demultiplexer. Using the appropriate key, the transport stream is decrypted, and elementary audio and video streams of the tuned channel are extracted and forwarded to audio and MPEG-2 video decoders, still in compressed form. The audio and MPEG-2 video decoders decompress the streams. Once decompressed, audio samples may be forwarded to an audio enhancement processor, which can enhance the samples in various ways, e.g. by applying Dolby Virtual Speaker™ technology, surround sound technology, or by performing sample rate conversion, before the samples are ultimately converted to sound by speakers. Dolby® Virtual Speaker™ technology is a trademark of Dolby Laboratories, Inc. Decompressed video frames, on the other hand, may be forwarded to a video and graphics post-processor, which can process the video frames/fields in various ways, e.g. by performing color management and contrast control, before they are ultimately displayed as images on a screen. For certainty, “video” refers to the program being watched, while “graphics” refers to, e.g., closed captioning, which is blended into the video.
In addition to stipulating that cable-compatible DTVs are to have a HOST-POD interface, the Digital Cable Plug and Play Report and Order also stipulates that cable-compatible DTVs are to have Digital Visual Interface (DVI) or High Definition Multimedia Interface (HDMI™) connectors, e.g. on the rear panel of the DTV device. The term HDMI™ is trademarked by HDMI Licensing, LLC. The purpose of these connectors is to permit devices that generate digital audio/video signals, such as Digital Versatile Disc (DVD) players for example, to be connected to the DTV, for purposes of presenting the generated digital audio/video signals at the DTV without any need for digital-to-analog (D/A) conversion (which could result in image and/or sound quality degradation). The United States government is increasing the percentage of televisions through government mandates such as the FCC's Digital Cable Plug and Play Report and Order. In order to be labelled as “Digital Cable Ready”, a television will be required to have such interfaces over the coming years. Ultimately, each DTV will have either a DVI connector or an HDMI™ connector. For clarity, the term “DVI/HDMI™ connector” is used herein to refer to either one of these types of connectors.
In a DTV having a DVI/HDMI™ connector, the received signal is an uncompressed video signal, in accordance with the DVI and/or HDMI™ specifications. Signals carried over the HDMI™ connector can also transport uncompressed or compressed audio signals while simultaneously transporting uncompressed video signals. The DVI specification was developed by Digital Display Working Group and can be found at ddwg.org/lib/dvi—10.pdf. The HDMI™ specification is developed by the HMDI Licensing, LLC and can be found at www.hdmi.org/manufacturer/specification.asp. Accordingly, the received digital audio/video signals bypass the above-described audio and video decoders, which perform decompression, as well as the transport demultiplexer. Instead, the digital audio and video signals received at the DVI/HDMI™ connector may be communicated directly to the audio decoder (in the case of compressed audio) or audio enhancement processor (for uncompressed audio), while digital video signals are communicated directly to the video and graphics post-processor, respectively.
If an enterprise other than a cable provider, such as a telecommunications service provider, is desirous of providing new services (e.g., new audio and/or visual content) for presentation at a cable compatible DTV having a DVI/HDMI™ connector, that enterprise faces a dilemma. On one hand, if it is desired for the new service to be received at the DVI/HDMI™ connector, it would be necessary to transmit the relevant video signals in an uncompressed state, which would disadvantageously consume large amounts of bandwidth and therefore limit the amount of content which could be provided. On the other hand, if it is desired for the new service to be received at the existing cable input to the DTV device, this may be technologically infeasible because the modulation, and tuning schemes of the enterprise may be incompatible with those of the cable provider and because the physical medium of the enterprise may be something other than a coaxial cable.
A provider of new services could develop a standalone set-top box which decompresses new programming and sends it to the DTV in uncompressed form via a DVI/HDMI™ connector for display. However a dedicated set-top box is expensive to develop and disadvantageously introduces yet another device into the large set of audio/video components that may already exist in the typical home.